Gas scrubber

ABSTRACT

The instant invention relates to a gas scrubber for cleaning dirty gas comprising an enclosed vessel having bottom, top and side walls, means dividing said vessel into upper and lower compartments, the bottom portion of said lower compartment defining a settling basin, at least one substantially vertically disposed open-ended gas collecting tube extending through said dividing means into both said compartments, an atomizing nozzle in said lower compartment positioned below each said gas collecting tube so as to discharge a mixture of a scrubbing liquid and a compressed gas upwardly into each said gas collecting tube, and means for circulating scrubbing liquid from said settling basin to said atomizing nozzle.

United States Patent [451 Mar. 28, 1972 Lincoln GAS SCRUBBER [72]Inventor: Roland L. Lincoln, Macungie, Pa.

[73] Assignee: Fuller Company, Catasaugua, Pa.

[22] Filed: Apr. 22, 1970 [21] Appl. No.: 30,670

[52] US. Cl ..55/228, 55/249, 55/468,

[51] Int. Cl ..B0ld 47/00 [58] Field ofSearch ..55/248, 249, 228, 256,468; 261/117, 76, 78 A [56] References Cited UNITED STATES PATENTS1,781,742 11/1930 Anglemeyer ..55/248 X 2,233,520 3/1941 Vigan ....55/249 X 3,444,668 5/1969 Masuda ....55/228 X 3,464,189 9/1969 Mergenthaler..55/468 X Sigalos [57] ABSTRACT The instant invention relates to a gasscrubber for cleaning dirty gas comprising an enclosed vessel havingbottom, top and side walls, means dividing said vessel into upper andlower compartments, the bottom portion of said lower compartmentdefining a settling basin, at least one substantially verticallydisposed open-ended gas collecting tube extending through said dividingmeans into both said compartments. an atomizing nozzle in said lowercompartment positioned below each said gas collecting tube so as todischarge a mixture of a scrubbing liquid and a compressed gas upwardlyinto each said gas collecting tube, and means for circulating scrubbingliquid from said settling'basin to said atomizing nozzle.

12 Claims, 2 Drawing Figures GAS SCRUBBER BACKGROUND OF THE INVENTIONHigh energy, high efficiency scrubbers are necessary for the mosteffective removal of dirt and other particulate materials from dirtygas. Such scrubbers require that certain basic conditions be met. Theseare that there be a very high differential velocity between thescrubbing liquid and the dirty gas to be cleaned, that there be a verylarge scrubbing liquid surface, and that there bea very high turbulencebetween the dirty gas and the scrubbing liquid surface. Other factors,of course, such as cost, power, space, maintenance and reliability areto be considered but the three basic conditions set forth above areessential for high efficiency. Such efficiency is particularly needednow as more stringent regulations are being invoked with respect to thecleaning of dirty gases before they are vented to the atmosphere inorder to prevent air pollution.

Presently there are two main types of commercial installations for thescrubbing of dirty gases. These are broadly classified as Venturi typescrubbers and flooded disc type scrubbers. In both, an induced draft fanis required to overcome the pressure loss of the gas as it passesthrough the scrubber and exhaust system. Because of the temperature ofthe gases and the dust loading in them,.particularly as such gases comefrom furnaces, it is necessary to locate the induced draft fan after thescrubber. This requires high energy and fan speed in order to move thegas through the scrubber at the desired speed in order to obtain thehigh differential velocity between the scrubbing fluid and the gas to becleaned. Such high fan speeds are exceedingly dangerous and result inexcessive scrubber shutdowns when moisture or dirt buildup on the fanblade causes imbalance of the fan.

Moreover, with Venturi type scrubbers, there is a limited gas volumerange that can be used at high efficiency without employing a variablethroat area. In addition, in suchVenturi type scrubbers, the scrubbingfluid is added at low velocity and at right angles to the flow of thedirty gas and adds nothing to the turbulence or differential velocityrequired to clean the gas but actually consumes energy from the highvelocity gas stream.

These recognized deficiencies of Venturi type scrubbers have led to theuse of flooded disc scrubbers which overcome some of the drawbacks ofthe Venturi type. Here, high gas velocity is still used but an abruptexpansion provides the desired high turbulence. Still, the scrubbingfluid is introduced at low velocity and at right angles to the gas flowand thus tends to consume some energy from the high velocity gas stream.Also, the energy required to be added to the gas volume results in thefan troubles common to the Venturi type device and the flooded discscrubber still requires adjustment of moving parts within the scrubberfor any change of gas volume.

SUMMARY OF THE INVENTION A gas scrubber has now been found whicheliminates the need for high fan speeds to build up high gas velocityand which permits the reuse of dirty scrubbing liquid without concern asto plugging of the spray nozzle through which clean scrubber fluid isdischarged against the dirty gas stream.

Briefly stated, the invention comprises a gas scrubber comprising anenclosed vessel having bottom, top and side walls, means dividing saidvessel into upper and lower compartments, dirty gas inlet means in saidupper compartment, clean gas outlet means in said lower compartment, atleast one substantially vertically disposed open-ended gas collectingtube extending through said dividing means into both said compartments,the inside of each gas collecting tube being substantially completelyopen throughout its length the bottom portion of said lower compartmentbelow the bottom end each of said gas collection tube defining asettling basin, at least one atomizing nozzle, and means for circulatingscrubbing liquid from said settling basin to each atomizing nozzle,andmeans for supplying compressed gas to each atomizing nozzle foratomizing the scrubbing liquid and accelerating it to a high velocity,each atomizing nozzle being positioned in said lower compartment below agas collecting tube for discharging a mixture of atomized scrubbingliquid and compressed gas upwardly into said gas collecting tubecountercurrent to the flow of dirty gas whereby high energy contact isachieved between the dirty gas and the atomized scrubbing liquid.

BRIEF DESCRIPTION OF DRAWINGS The invention will be more particularlydescribed with reference to the illustrative embodiments thereof,wherein:

FIG. 1 is a sectional view of a gas scrubber of the instant invention;and

FIG. 2 is a top plan view of a modular form of the instant invention.

DETAILED DESCRIPTION Referring to the drawings, there is shown a gasscrubbing vessel generally indicated as 10 comprising top 11, bottom 12and side walls 13, preferably made of metal. A division plate 14attached to the walls 13 divides the vessel into upper 15 and lower 16compartments. While shown in a sloping posi tion, the plate 14 may alsobe in a substantially horizontal position.

An opening 17 is provided in the upper compartment 15 for connectionwith tubing (not shown) connecting the scrubber to the source of dirtygas. A clean gas outlet 18 is provided in the side wall of the lowercompartment 16 for removal of the clean gas from the scrubber. In somecases it may be desired to pass the clean gas through a conventionalmist eliminator in order to insure that any scrubbing liquid entrainedby the gases is removed before the gas is further used or vented to theatmosphere. A gas collecting chamber 19 is vertically disposed in thevessel and extends through the division plate 14. It is open at bothends, and in a preferred embodiment shown in the drawings is flared atits inlet portion 20.

The division plate 14 may be provided with a scrubbing liquid conduit 21which, as hereinafter described, conveys scrubbing fluid settling in theupper compartment 15 to a settling basin. The bottom 12 of the vessel 10is sloped and is provided with a sludge removal opening 22 from whichthe sludge (dirt and other particulate materials) removed from the gascan be removed from the vessel. The sloping bottom 12 of the vessel 10and the side walls 13 combine in the lower portion of the compartment 16to form a settling basin in which scrubbing liquid is kept at apredetermined level by means of a float valve 23 which permits theaddition of makeup scrubbing liquid to maintain the desired level.

An atomizing nozzle 24 having its discharge orifice 25 above the levelof the scrubbing liquid 26 in the settling basin is positioned in thelower compartment so as to be able to discharge a mixture of scrubbingfluid and compressed gas from the orifice 25 directly into the gascollecting chamber 19. The atomizing nozzle 24 is connected by means ofsuitable piping 27 to a recirculating pump 28 and to a discharge opening29 for the scrubbing liquid in the settling basin.

The scrubber may be provided with a deflector plate 30 mounted to thewalls which acts to deflect any of the scrubbing liquid which may notact on the gas as it passes through the gas collecting chamber 19.

The atomizing nozzle 24 has a flared discharge orifice 25 and arestricted throat 31. Passing upwardly in the nozzle to a point justbelow the restricted throat 31 is tube 32 for compressed air. Inoperation, as the scrubbing liquid comes to the restricted throat 31 theenergy of the compressed air fed through the tube 32 atomizes the liquidinto a fine mist and transports it with sufficient energy upwardlythrough and into the gas collecting chamber 19 where it comes intocountercurrent contact with the downwardly flowing dirty gas.

The operation of the scrubber will be largely evident from the foregoingdescription but will be further described in connection with a scrubberhaving a nominal gas capacity therethrough of 25,000 c.f.m. For suchcapacity a 22-inch diameter gas collecting chamber 19 is used and thefan used to draw the gas through the scrubber need only be of a size toassure a pressure drop through the scrubber of less than l inches.Consequently, no extra high speed fan is required and the danger of anyfan blowup is materially reduced.

Under these operating conditions, the downward velocity of the gas(9,500/min.) is not adequate to obtain high efficiency cleaning byitself. The atomizing nozzle 24, however, is designed to accelerate thewater droplets to a velocity of over 30,000 f.p.m. At the nominaldownward gas velocity of 9,500 feet per minute and an upward watervelocity of 30,000 f.p.m., there is an impact velocity of 39,500 f.p.m.or over 650 feet per second well above the usual venturi velocity of 400feet per second. It is recognized that this velocity will not bemaintained but will be slowed down by the impact of the water dropletson the gas. It is this differential velocity which gives the highcollection efficiency.

By putting the energy into the water instead of the gas, there isobtained the same impact and energy but at a materially reduced induceddraft wheel tip speed. This reduces the danger of abrupt failure whenmud is deposited on the wheel, an unfortunately too common an experiencein existing scrubbers.

By using compressed air to provide the high velocity of the waterdroplets, the use of high pressure water pumps and piping is avoided asis the need for small diameter ports. The combination of small ports andhigh velocity of water through them is troublesome when recirculatingdust laden water with possible corrosive fluids dissolved in the water.With the atomizing type nozzle, the air is compressed clean and permitsopenings of at least one-half inch in both the air and water ports inthe nozzle. The use of the compressed air also permits break up of thewater into a fine mist with a very large surface area, a necessaryrequirement for high efficiency scrubbing. The introduction of thenecessary energy through the air compressor instead of the fan thus hasmany advantages.

The water supplied to the nozzle is supplied by recirculating pump 28 asit is received from the discharge opening 29. This minimizes the amountof water needed to operate the scrubber. Make up water as needed issupplied through float valve 23. Scrubbing water that collects in theupper compartment [5 settles on the division plate 14 and is carriedback to the settling basin through conduit 21.

As the water in the settling basin is in a relatively quiescentcondition, the dirt and particulate matter entrapped therein duringcontact of the water with the dirty gas settle to the bottom 12 of thevessel and are removed through sludge removal opening 22.

One of the existing problems of scrubber application is the necessity ofmaintaining high efficiency with a wide range of gas volumes without theundesirable mechanical movement of parts. With the instant inventionthis requirement is met automatically. Even a reduction of percent ofnominal volume gives an impact velocity of (20 percent of 9,500) 30,000or 3 l ,900 f.p.m. or 530 feet per second. The instant invention at 20percent volume gives a higher differential velocity than other designsat full volume.

Referring to FIG. 2, there is shown a multiple scrubber assembly 40consisting of three vessels each having gas collecting chambers 41 andother elements of the scrubber as described above. A common intakemanifold 42 connecting with the source of dirty gas conveys the gas tothe individual units of the assembly 40 and a common exhaust manifold 43conveys the scrubbed gas away from the individual units.

Thus, scrubber capacity can be varied by either varying the diameter ofthe gas collector chambers, or forming multiple scrubber assemblies, ora combination of both.

If desired, the deflector 30 could be eliminated. If this is done, theinlet 17 should be at an angle to the housing so that liquid whichtravels through the gas collecting chamber will not enter the tubingassociated with the opening 17. It may also be desirable to lower theheight of the housing so that the top 11 is in the position of thedeflector 30.

The scrubbing liquid conduit can be eliminated by decreasing the heightof the gas collecting chamber 19 so that its upper surface is flush withthe division plate 14. In this instance, the chamber 19 will act as aliquid conduit for returning liquid which reaches upper compartment 15to the settling basin.

As a further modification, the recirculating pump 28 can be eliminated.in order to accomplish this, the opening 29 is closed and the pipingsection 27 leading from the opening 29 to the pump 28 is eliminated. Thepiping section 27 leading from the pump 28 to the nozzle 24 issubstantially eliminated. The pipe section 27 within the setting basinis cut off so that it is open to the scrubbing liquid at a point belowthe surface of the liquid and above the point of heavy concentration ofsludge. The level ofliquid in the settling basin is maintained so thatit is slightly above the outlet of compressed air tube 32. As compressedair exists from tube 32 it will atomize the liquid and spray it towardsthe chamber 19. Liquid will be drawn into the nozzle by the action ofthe compressed air.

It will be understood that it is intended to cover all changes andmodifications of the disclosure of the invention herein chosen for thepurpose of illustration which do not constitute departures from thespirit and scope of the invention.

What is claimed is:

1. A gas scrubber comprising an enclosed vessel having a bottom, top andside walls, means dividing said vessel into upper and lowercompartments, dirty gas inlet means in said upper compartment, clean gasoutlet means in said lower compartment, at least one substantiallyvertically disposed openended gas collecting tube mounted in saiddividing means and extending into at least one of said compartments, theinside of each said gas collecting tube being substantially completelyopen throughout its length, the bottom portion of said lower compartmentbelow the bottom end of each said gas collecting tube defining asettling basin, at least one atomizing nozzle, means for circulatingscrubbing liquid from said settling basin to each atomizing nozzle, andmeans for supplying compressed gas to each atomizing nozzle foratomizing the scrubbing liquid and accelerating it to a high velocity,each atomizing nozzle being positioned in said lower compartment below agas collecting tube for discharging a mixture of atomized scrubbingliquid and compressed gas upwardly into said gas collecting tubecountercurrent to the flow of dirty gas whereby high energy contact isachieved between the dirty gas and the atomized scrubbing liquid.

2. The gas scrubber according to claim 1 further comprising means formaintaining a substantially constant level of scrubbing liquid in saidsettling basin.

3. The gas scrubber according to claim 2 wherein the bottom of saidvessel is sloped and contains, at about its lowest point, means forremoval of sludge from said settling basin.

4. The gas scrubber according to claim 2 including scrubbing liquidreturn means connecting said upper compartment with the scrubbing liquidin said settling basin for return of scrubbing liquid from said uppercompartment to said settling basin.

5. The gas scrubber according to claim 2 wherein the discharge orificeof the atomizing nozzle is above the surface of the scrubbing liquid inthe settling basin and the nozzle comprises a hollow tube having adischarge orifice and said means for supplying compressed gas to saidatomizing nozzle includes means, in said hollow tube for delivering acompressed gas to a point below said discharge orifice.

6. The gas scrubber according to claim 2 wherein the discharge orificeof the atomizing nozzle is above the surface of the scrubbing liquid inthe settling basin and the nozzle comprises a hollow tube having aflared discharge orifice, a restricted throat downstream from saidorifice, and means in said hollow tube for delivering compressed gas toa point below said restricted throat.

7. The gas scrubber according to claim 6 including at least oneopen-ended conduit affixed to said dividing means and extendingdownwardly therefrom a point below the surface of the scrubbing liquidin said settling basin and sludge removal means in the bottom of thesettling basin.

8. A gas scrubber comprising a series of scrubbers according to claim 2wherein the dirty gas inlet means for each individual scrubber is influid flow communication with means connected to the source of dirty gasand the clean gas outlet means for each individual scrubber is in fluidflow communication with a common exhaust means.

9. A gas scrubber comprising an enclosed vessel having bottom, top andside walls, means dividing said vessel into first and secondcompartments, dirty gas inlet means in said first compartment, at leastone open-ended gas collecting tube mounted in said dividing means andextending into at least one of said compartments, the inside of said gascollecting tube being substantially completely open throughout itslength, the lower portion of said second compartment below one end ofsaid gas collecting tube defining a settling basin, an atomizing nozzlepositioned so as to discharge a scrubbing liquid upwardly into each saidcollecting tube countercurrent to the flow of dirty gas whereby highenergy contact is achieved between the dirty gas and the scrubbingliquid, and means for circulating scrubbing liquid from said settlingbasin to said atomizing nozzle.

10. The gas scrubber according to claim 9 wherein said atomizing nozzlecomprises a hollow tube having a discharge orifice and means in saidhollow tube for delivering a compresed gas to a point below saiddischarge orifice whereby a mixture of scrubbing liquid and compressedgas is discharged into each said gas collecting tube.

11. A gas scrubber comprising a vessel having bottom, top and sidewalls, means dividing said vessel into first and second compartments,dirty gas inlet means in said first compartment,

clean gas outlet means in said second compartment, at least oneopen-ended gas collecting tube mounted in said dividing means; the lowerportion of said second compartment below said gas collecting tubedefining a settling basin, an atomizing nozzle, and means for supplyinga compressed gas to said atomizing nozzle for atomizing the scrubbingliquid and accelerating the atomized scrubbing liquid to a highvelocity; said atomizing nozzle being positioned for discharging amixture of compressed gas and scrubbing liquid into each gas collectingtube countercurrent to the flow of dirty gas whereby high energy contactis achieved between the dirty gas and the atomized scrubbing liquid.

12. A gas scrubber comprising a vessel, at least one gas collecting tubemounted in and having an open end communicating with said vessel; saidgas collecting tube being substantially completely open throughout itslength; dirty gas inlet means communicating with said tube; clean gasoutlet means communicating with said vessel and separated from directcommunication with the dirty gas inlet means; said vessel defining asettling basin below said tube; an atomizing nozzle; means for supplyinga scrubbing liquid to said atomizing nozzle; and means for supplying acompressed gas to said atomizing nozzle for atomizing the scrubbingliquid and accelerating the atomized scrubbing liquid to a highvelocity; said atomizing nozzle being positioned for discharging amixture of compressed gas and atomized scrubbing liquid into the gascollecting tube countercurrent to the flow of dirty gas whereby highenergy contact is achieved between the dirty gas and the atomizedscrubbing liquid.

1. A gas scrubber comprising an enclosed vessel having a bottom, top andside walls, means dividing said vessel into upper and lowercompartments, dirty gas inlet means in said upper compartment, clean gasoutlet means in said lower compartment, at least one substantiallyvertically disposed open-ended gas collecting tube mounted in saiddividing means and extending into at least one of said compartments, theinside of each said gas collecting tube being substantially completelyopen throughout its length, the bottom portion of said lower compartmentbelow the bottom end of each said gas collecting tube defining asettling basin, at least one atomizing nozzle, means for circulatingscrubbing liquid from said settling basin to each atomizing nozzle, andmeans for supplying compressed gas to each atomizing nozzle foratomizing the scrubBing liquid and accelerating it to a high velocity,each atomizing nozzle being positioned in said lower compartment below agas collecting tube for discharging a mixture of atomized scrubbingliquid and compressed gas upwardly into said gas collecting tubecountercurrent to the flow of dirty gas whereby high energy contact isachieved between the dirty gas and the atomized scrubbing liquid.
 2. Thegas scrubber according to claim 1 further comprising means formaintaining a substantially constant level of scrubbing liquid in saidsettling basin.
 3. The gas scrubber according to claim 2 wherein thebottom of said vessel is sloped and contains, at about its lowest point,means for removal of sludge from said settling basin.
 4. The gasscrubber according to claim 2 including scrubbing liquid return meansconnecting said upper compartment with the scrubbing liquid in saidsettling basin for return of scrubbing liquid from said uppercompartment to said settling basin.
 5. The gas scrubber according toclaim 2 wherein the discharge orifice of the atomizing nozzle is abovethe surface of the scrubbing liquid in the settling basin and the nozzlecomprises a hollow tube having a discharge orifice and said means forsupplying compressed gas to said atomizing nozzle includes means, insaid hollow tube for delivering a compressed gas to a point below saiddischarge orifice.
 6. The gas scrubber according to claim 2 wherein thedischarge orifice of the atomizing nozzle is above the surface of thescrubbing liquid in the settling basin and the nozzle comprises a hollowtube having a flared discharge orifice, a restricted throat downstreamfrom said orifice, and means in said hollow tube for deliveringcompressed gas to a point below said restricted throat.
 7. The gasscrubber according to claim 6 including at least one open-ended conduitaffixed to said dividing means and extending downwardly therefrom to apoint below the surface of the scrubbing liquid in said settling basinand sludge removal means in the bottom of the settling basin.
 8. A gasscrubber comprising a series of scrubbers according to claim 2 whereinthe dirty gas inlet means for each individual scrubber is in fluid flowcommunication with means connected to the source of dirty gas and theclean gas outlet means for each individual scrubber is in fluid flowcommunication with a common exhaust means.
 9. A gas scrubber comprisingan enclosed vessel having bottom, top and side walls, means dividingsaid vessel into first and second compartments, dirty gas inlet means insaid first compartment, at least one open-ended gas collecting tubemounted in said dividing means and extending into at least one of saidcompartments, the inside of said gas collecting tube being substantiallycompletely open throughout its length, the lower portion of said secondcompartment below one end of said gas collecting tube defining asettling basin, an atomizing nozzle positioned so as to discharge ascrubbing liquid upwardly into each said collecting tube countercurrentto the flow of dirty gas whereby high energy contact is achieved betweenthe dirty gas and the scrubbing liquid, and means for circulatingscrubbing liquid from said settling basin to said atomizing nozzle. 10.The gas scrubber according to claim 9 wherein said atomizing nozzlecomprises a hollow tube having a discharge orifice and means in saidhollow tube for delivering a compressed gas to a point below saiddischarge orifice whereby a mixture of scrubbing liquid and compressedgas is discharged into each said gas collecting tube.
 11. A gas scrubbercomprising a vessel having a bottom, top and side walls, means dividingsaid vessel into first and second compartments, dirty gas inlet means insaid first compartment, clean gas outlet means in said secondcompartment, at least one open-ended gas collecting tube mounted in saiddividing means; the lower portion of said second compartment below saidgas collecting tube defining a settling basin, an atomizIng nozzle, andmeans for supplying a compressed gas to said atomizing nozzle foratomizing the scrubbing liquid and accelerating the atomized scrubbingliquid to a high velocity; said atomizing nozzle being positioned fordischarging a mixture of compressed gas and scrubbing liquid into eachgas collecting tube countercurrent to the flow of dirty gas whereby highenergy contact is achieved between the dirty gas and the atomizedscrubbing liquid.
 12. A gas scrubber comprising a vessel, at least onegas collecting tube mounted in and having an open end communicating withsaid vessel; said gas collecting tube being substantially completelyopen throughout its length; dirty gas inlet means communicating withsaid tube; clean gas outlet means communicating with said vessel andseparated from direct communication with the dirty gas inlet means; saidvessel defining a settling basin below said tube; an atomizing nozzle;means for supplying a scrubbing liquid to said atomizing nozzle; andmeans for supplying a compressed gas to said atomizing nozzle foratomizing the scrubbing liquid and accelerating the atomized scrubbingliquid to a high velocity; said atomizing nozzle being positioned fordischarging a mixture of compressed gas and atomized scrubbing liquidinto the gas collecting tube countercurrent to the flow of dirty gaswhereby high energy contact is achieved between the dirty gas and theatomized scrubbing liquid.